[School of Engineering PhD Scholarships] From Solid to Flow: Understanding Yielding in Soft Materials

About the project

About the Project Yield-stress materials are everywhere: in foods, cosmetics, pharmaceuticals, coatings, construction materials, pastes, inks and many advanced manufacturing processes. Examples include mayonnaise, yoghurt, toothpaste, hair gels, creams, paints, cement pastes and printing inks. These materials can behave like solids when weakly forced, yet flow like liquids once a critical condition is reached. This apparently simple solid-to-fluid transition has major practical consequences, but its underlying mechanics remain surprisingly poorly understood. This PhD project will investigate what it really means for a soft material to yield. Even below the conventional yield stress, materials such as gels, concentrated emulsions and dense suspensions can display slow creep, nonlinear deformation and apparent slip at solid boundaries. These effects complicate both the interpretation of experiments and our ability to predict how such materials behave during processing and use. The project builds on recent research within our groups on sub-yield dynamics, wall slip and elastic behaviour [1–5]. This work has revealed unexpected deformation below the apparent yield point, limitations of existing constitutive models, and the major influence that slip can have on confined flows. The successful candidate will help develop the next stage of this research: establishing a more complete mechanical description of the transition from solid-like behaviour to flow. The project will combine advanced experimental rheology with physical and mathematical modelling. Shear-rheometry experiments will investigate creep, recovery, nonlinear oscillatory behaviour and apparent slip, while variations in sample dimensions and surface conditions will help distinguish bulk deformation from boundary effects. Extensional rheology will provide a complementary perspective, using techniques such as rheometer-based extension, capillary-breakup rheometry (CaBER) and cross-slot/OSCER measurements to investigate whether yielding follows common principles under different deformation modes. The experimental results will then be used to test and improve constitutive models of yield-stress materials. A key aim will be to connect ideas from rheology and solid mechanics, developing more accurate models capable of describing the progression from predominantly recoverable deformation to fully developed flow. The project is suitable for candidates from Chemical Engineering, Physics, Mechanical Engineering, Applied Mathematics or related quantitative disciplines. The student will develop a combination of experimental, computational and modelling skills that are highly sought after in sectors including personal care, food, pharmaceuticals, consumer products, formulated products, advanced manufacturing and materials processing. Training in rheometry, continuum mechanics, data analysis, constitutive modelling, numerical methods and scientific computing will provide a strong foundation for careers in both industrial R&D and academic research. References: [1] Phys. Rev. Lett. 136, 164001 (2026); [2] J. Non-Newtonian Fluid Mech. 338, 105407 (2025); [3] arXiv:2609.12229 (2026); [4] Appl. Phys. Lett. 128, 242703 (2026); [5] Chem. Eng. Sci. 321, 123005 (2026). This project is expected to start in September 2027. Before you apply: We strongly recommend that you contact the supervisors for this project before you apply. How to apply: To be considered for this project you must complete a formal application through our online application portal. If you already have an applicant account this link will directly open an application for PhD School of Engineering Scholarships . If you don’t already have an applicant account, please follow the instructions here. . When applying, please specify the full title and supervisor/s of the project, details of your previous study, and names and contact details of two referees. You must also upload a Supporting Statement describing the motivation to apply to the project, your CV and transcripts of awarded and in-progress university qualifications . Please note late or incomplete applications will not be considered. Equality, diversity and inclusion are fundamental to the success of The University of Manchester and central to all our activities. A diverse research community strengthens creativity, productivity and quality, while increasing the societal and economic impact of our work. We welcome applicants from all career paths, backgrounds and sections of the community, regardless of age, disability, ethnicity, gender, gender expression, sexual orientation or transgender status. We welcome applications from candidates returning to study after a career break or experience in other roles. Flexible study arrangements may be available, including part-time study at 50%, 60% or 80%, subject to the requirements of the project and funder. Eligibility : The standard academic entry requirement for this PhD is an upper second-class (2:1) honours degree (or international equivalent) in Chemical Engineering, Physics, Mechanical Engineering, Applied Mathematics OR any upper-second class (2:1) honours degree and a Master’s degree at merit (or international equivalent) in Chemical Engineering, Physics, Mechanical Engineering, Applied Mathematics. Previous experience of laboratory rheology, fluid mechanics, scientific programming or computational modelling is desirable. This project will remain open until filled. If your application is submitted by 1 st November 2026, you can expect a decision by 18 th December 2026. If your application is submitted by 15 th January 2027, you can expect a decision by 30 th March 2027. Self or externally funded students can also be considered for this project. FSESoE

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